In general, in an image reading device such as a scanner that can read an image from a document sheet mounted on a document sheet mounting surface, a reading unit and a control portion are connected by a cable, wherein the reading unit performs an image reading operation by moving in a sub scanning direction. Meanwhile, with a configuration where the cable in use is folded vertically in the housing of the image reading device, part of the upper portion of the cable may hang down and contact part of the lower portion, allowing a crosstalk to occur, which may impair the control of the control portion on the reading unit. Such a contact between different parts of the cable can be restricted by securing a sufficient interval in the vertical direction between the control portion and the reading unit. However, in that case, the housing of the image reading device increases in size. With regard to this problem, there is known a configuration where the reading unit includes a clamp portion for supporting the cable (see, for example, PTL 1).